Stress-induced Behaviour in Rams of Three Different Sheep (Ovis aries) Breeds: Indicator of Welfare?

Abstract

Growing importance of and concern for the welfare of farm animals within production systems has been the basis for an enormous amount of scientific studies. The goal of the present study was to investigate whether both vocal and social behaviour of sheep, under specific stress-inducing situations, could be used as an indicator of the animals’ welfare status. Two separate experiments were carried out with 2-3 year old adult rams. The animals were of three breeds, namely Barbados Blackbelly Cross, Local Garut and Composite Garut. In the first experiment twelve clinically healthy animals, four from each breed, were subjected to three different levels of social isolation. The animals were held completely alone, in the presence of a human and alone in a group pen adjacent to a pen with conspecifics. During the isolation sessions both vocal and locomotive behaviour of each animal were recorded. The recorded calls were acoustically analyzed using specialized acoustic software. The results showed that the levels of isolation were characterized by very specific behavioural responses with an increased amount of locomotor activity and vocalization in partially isolated animals. The animals that were completely isolated showed a higher amount of inactive behaviour. No specific differences were found in the behaviour of animals that were held completely alone and the ones which were in the presence of a human observer. Acoustic analysis of the recorded calls showed significant differences in a number of temporal and structural features. Spectral analysis revealed the most notable differences in the amount of sound energy integrated in the calls. Differences were found in both locomotive and vocal behaviour based on isolation level and breed....dst